There is a so-called wireless backhaul technology used for connection between areas, where no wire reaches or a wired cable cannot be laid, such as remote islands or depopulated regions. As one technique, there is known a technology in which a relay device is used to connect a base station and a terminal to each other with wireless communication (for example, see JP-A-2012-205091).
The relay device includes a service-side (for a service channel) wireless device that performs wireless communication with the terminal and a backhaul wireless device that communicates with the base station. After installation of the relay device, the relay station tries a call to the base station, and a backhaul wireless channel is established between the relay station and the base station. At this time, the relay device is used as a terminal and performs a normal calling process. It is assumed herein that the base station and the relay device after the installation are fixed to not be movable.